What is a zygote?

A zygote is accurately defined as a cell produced from the fusion of two gametes, which are the sperm and egg cells. This process occurs during fertilization, and it marks the initial stage of development of a new organism. The zygote contains a complete set of genetic material, half from the mother and half from the father, and it will undergo numerous cell divisions and differentiations as it develops into an embryo.

The other choices describe different medical terms or structures. A type of skin lesion refers to irregularities or changes in the skin, while a small sac filled with serous fluid indicates something like a blister or cyst. A rounded elevation with fluid describes a structure such as a vesicle or bulla. None of these terms relate to the concept of a zygote, which is specific to reproductive biology and the development of an embryo.